The invention relates generally to storing data, and more specifically, to asymmetric storage data distribution.
Storing ever increasing data volumes has been and continues to be a challenge in data centers. With the rise of the big data phenomenon and the requirement to store not only structured or semi-structured data but also unstructured data, data from sensors of any kind in a digital format, a proper management of storage system life-times becomes a pure necessity. This need is even more increased in days in which new storage technologies are introduced in data centers, but also in the private/personal sector. Some of these new storage technologies include solid state devices (SSD) of phase change memory systems (PCM), which may have a different time-dependent characteristic of storing data as compared to spinning magnetic disks. One effect that characterizes SSDs or PCM storage systems, and in some cases also dynamic RAM (random access memory) storage systems, is that these systems show an aging effect or a wear level. These effects undermine a long-term reliability of the storage systems, or in other words, these systems allow only a limited number of writes before they need to be replaced.
Existing RAID (redundant array of independent disks) controllers attempt to equally distribute data to all available storage systems for a maximum performance. When the storage system is an SSD and when such an SSD fails, the data on the failing device is reconstructed from the other members onto a hot-spare storage system. This works well for disks which fail without much warning.
However, SSDs and also PCM systems as well as others fail in different ways. The total number of writes is limited due to physical effects of the underlying storage elements. In case of a typical equal distribution of write excesses to the storage system, more or less all storage elements should fail typically at the same time. This may be seen as a real threat to storage systems. Hence, there is a need to ensure proper maintainability of aging storage systems in order to be compliant with RAS standards (reliability, availability, and serviceability) in high performance and highly reliable computing systems.